Arthimetic sequences
An arithmetic sequence is one where the difference between one term and the next is always the same.
For arithmetic sequences, to go from any term to the next the rule is to always add or subtract the same value.
The number added (or subtracted) at each stage (i.e the rule) of the arithmetic sequence is called the common difference.
How to work out the next term in a sequence
Step 1
- write out your sequence:
- 8, 11, 14, 17...
Step 2
- find the common difference (the difference between each pair of numbers)
- write it down:
- 8 (+3) 11 (+3) 14 (+3) 17...
Step 3
- use the common difference to find the next number in the sequence:
- 17 (+3) = 20
Question
Now try steps 1-3 on a new arithmetic sequence:
70, 60, 50, 40 ...
Step 1
- write out your sequence:
- 70, 60, 50, 40 ...
Step 2
- find the common difference (the difference between each pair of numbers)
- the common difference is -10 because 10 is subtracted (taken away) from each term (number) to give the next term in the sequence
- write it down:
- 70 (-10) 60 (-10) 50 (-10) 40...
Step 3
- use the common difference to find the next number in the sequence:
- 40 (– 10) = 30
The next term in the sequence will be 30.